Good article on Survival Blog about the problems in defending a large property
My thinking on this has always been : a large property is a large target.
I have always believed that the ideal situation would be a very small entrance to a belowground refuge behind the house off a dead-end street. Especially the sort of refuge that a couple hours of work could conceal so effectively it would appear to be an overgrown rubbish tip.
If you then burned the house down (or an event did it for you), you have what looks like an abandoned burned out shell with an overgrown rubbish pile in the back. You liberally dress the site with broken glass, sharp edges and barbed wire and before you know it the property is so discouraging and of so little apparent value that nobody bothers. A couple months of weed growth and you got a garbage tip with ivy on it. A self-sufficient refuge underground that only produces mild amounts of intermittent heat signature from a generator and otherwise has no sign of inhabitation whatsoever. A man who is hungry is not going to be shuffling through garbage piles covered with broken glass and barbed wire. There are a million more interesting targets of obvious opportunity.
Compare this with a large farm bounded by a fence. Everybody can see this is a target. It is like putting out a white flag for people who are starving. The very nature of the place makes it a subject of seige. If it has a road going to it then people will aim to drive their vehicles onto it.
I have heard people on DOOMSDAY PREPPERS talking about taking on people to work their farms who show up to raid it. Speaking for myself, this doesn't seem realistic. They are imagining a couple folks showing up. What about ten thousand people cruising around looking for easy targets of opportunity? Do they imagine they will remain in charge of the distribution of resources on their farms?
I foresee the only real safety lies in making yourself so small that nobody reliably can even be sure you exist.
Then you are dealing with a tiny minority of people who might accidentally stumble onto your shelter. They can be dealt with at that time in numbers you can cope with. Hopefully silently and with as little risk as possible.
It seems to me that running a conventional farm over an acre is just putting out a buglight for starving, desperate people. If it can be seen it is going to draw looters. If it cannot be identified until you're a meter away from the door or hatch, that's a very different kind of place to hide yourself.